docs: rewrite README with current infrastructure overview

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

README.md

@@ -1,11 +1,128 @@
 # nixos-servers
 
-Nixos configs for my homelab servers.
+NixOS Flake-based configuration repository for a homelab infrastructure. All hosts run NixOS 25.11 and are managed declaratively through this single repository.
 
-## Configurations in use
+## Hosts
 
-* ha1
-* ns1
-* ns2
-* template1
+| Host | Role |
+|------|------|
+| `ns1`, `ns2` | Primary/secondary authoritative DNS |
+| `ns3`, `ns4` | Additional DNS servers |
+| `ca` | Internal Certificate Authority |
+| `ha1` | Home Assistant + Zigbee2MQTT + Mosquitto |
+| `http-proxy` | Reverse proxy |
+| `monitoring01` | Prometheus, Grafana, Loki, Tempo, Pyroscope |
+| `jelly01` | Jellyfin media server |
+| `nix-cache01` | Nix binary cache |
+| `pgdb1` | PostgreSQL |
+| `nats1` | NATS messaging |
+| `auth01` | Authentication (LLDAP + Authelia) |
+| `vault01` | OpenBao (Vault) secrets management |
+| `media1` | Media services |
+| `template1`, `template2` | VM templates for cloning new hosts |
 
+## Directory Structure
+
+```
+flake.nix              # Flake entry point, defines all host configurations
+hosts/<hostname>/      # Per-host configuration
+system/                # Shared modules applied to ALL hosts
+services/              # Reusable service modules, selectively imported per host
+modules/               # Custom NixOS module definitions
+lib/                   # Nix library functions (DNS zone generation, etc.)
+secrets/               # SOPS-encrypted secrets (age encryption)
+common/                # Shared configurations (e.g., VM guest agent)
+terraform/             # OpenTofu configs for Proxmox VM provisioning
+terraform/vault/       # OpenTofu configs for OpenBao (secrets, PKI, AppRoles)
+playbooks/             # Ansible playbooks for template building and fleet ops
+scripts/               # Helper scripts (create-host, vault-fetch)
+```
+
+## Key Features
+
+**Automatic DNS zone generation** - A records are derived from each host's static IP configuration. CNAME aliases are defined via `homelab.dns.cnames`. No manual zone file editing required.
+
+**SOPS secrets management** - Each host has a unique age key. Shared secrets live in `secrets/secrets.yaml`, per-host secrets in `secrets/<hostname>/`.
+
+**Daily auto-upgrades** - All hosts pull from the master branch and automatically rebuild and reboot on a randomized schedule.
+
+**Shared base configuration** - Every host automatically gets SSH, monitoring (node-exporter + Promtail), internal ACME certificates, and Nix binary cache access via the `system/` modules.
+
+**Proxmox VM provisioning** - Build VM templates with Ansible and deploy VMs with OpenTofu from `terraform/`.
+
+**OpenBao (Vault) secrets** - Centralized secrets management with AppRole authentication, PKI infrastructure, and automated bootstrap. Managed as code in `terraform/vault/`.
+
+## Usage
+
+```bash
+# Enter dev shell (provides ansible, opentofu, openbao, create-host)
+nix develop
+
+# Build a host configuration locally
+nix build .#nixosConfigurations.<hostname>.config.system.build.toplevel
+
+# List all configurations
+nix flake show
+```
+
+Deployments are done by merging to master and triggering the auto-upgrade on the target host.
+
+## Provisioning New Hosts
+
+The repository includes an automated pipeline for creating and deploying new hosts on Proxmox.
+
+### 1. Generate host configuration
+
+The `create-host` tool (available in the dev shell) generates all required files for a new host:
+
+```bash
+create-host \
+  --hostname myhost \
+  --ip 10.69.13.50/24 \
+  --cpu 4 \
+  --memory 4096 \
+  --disk 50G
+```
+
+This creates:
+- `hosts/<hostname>/` - NixOS configuration (networking, imports, hardware)
+- Entry in `flake.nix`
+- VM definition in `terraform/vms.tf`
+- Vault AppRole policy and wrapped bootstrap token
+
+Omit `--ip` for DHCP. Use `--dry-run` to preview changes. Use `--force` to regenerate an existing host's config.
+
+### 2. Build and deploy the VM template
+
+The Proxmox VM template is built from `hosts/template2` and deployed with Ansible:
+
+```bash
+nix develop -c ansible-playbook -i playbooks/inventory.ini playbooks/build-and-deploy-template.yml
+```
+
+This only needs to be re-run when the base template changes.
+
+### 3. Deploy the VM
+
+```bash
+cd terraform && tofu apply
+```
+
+### 4. Automatic bootstrap
+
+On first boot, the VM automatically:
+1. Receives its hostname and Vault credentials via cloud-init
+2. Unwraps the Vault token and stores AppRole credentials
+3. Runs `nixos-rebuild boot` against the flake on the master branch
+4. Reboots into the host-specific configuration
+5. Services fetch their secrets from Vault at startup
+
+No manual intervention is required after `tofu apply`.
+
+## Network
+
+- Domain: `home.2rjus.net`
+- Infrastructure subnet: `10.69.13.0/24`
+- DNS: ns1/ns2 authoritative with primary-secondary AXFR
+- Internal CA for TLS certificates (migrating from step-ca to OpenBao PKI)
+- Centralized monitoring at monitoring01